The development of a flat display utilizing a liquid crystal (LCD) panel, PDP (Plasma Display Panel) and the like are being pursued actively today. In recent years, each manufacturer particularly directs the attention to the further thinning of such a flat display. For example, it is known that a backlight device irradiating light from the rear of a panel is required when a display utilizing the LCD panel is to be manufactured. To promote the thinning of the display, the thinning of the backlight device is also one important subject.
To achieve the thinning of the backlight device, proposed is a backlight system where light is emitted from an LED (Light Emitting Diode) toward an end face of a light guide plate (see Patent Document 1, for instance). Where the LED is placed beside the light guide plate as described above, it is possible to suppress the increase in thickness of the backlight device due to the light source. Also, when a separation distance between an incidence plane of the light guide plate and a light-emitting element is denoted by d and the distance between each light-emitting element is denoted by p, a backlight device meeting 0.2≦p≦d≦0.8p is proposed (see Patent Document 2, for instance).